linux-fsdevel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Souptick Joarder <jrdr.linux@gmail.com>
To: mawilcox@microsoft.com, ross.zwisler@linux.intel.com,
	viro@zeniv.linux.org.uk
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org
Subject: [PATCH v2] fs: dax: Adding new return type vm_fault_t
Date: Sat, 21 Apr 2018 22:44:42 +0530	[thread overview]
Message-ID: <20180421171442.GA17919@jordon-HP-15-Notebook-PC> (raw)

Use new return type vm_fault_t for fault handler. For
now, this is just documenting that the function returns
a VM_FAULT value rather than an errno. Once all instances
are converted, vm_fault_t will become a distinct type.

commit 1c8f422059ae ("mm: change return type to vm_fault_t")

There was an existing bug inside dax_load_hole()
if vm_insert_mixed had failed to allocate a page table,
we'd return VM_FAULT_NOPAGE instead of VM_FAULT_OOM.
With new vmf_insert_mixed() this issue is addressed.

vm_insert_mixed_mkwrite has inefficiency when it returns
an error value, driver has to convert it to vm_fault_t
type. With new vmf_insert_mixed_mkwrite() this limitation
will be addressed.

Signed-off-by: Souptick Joarder <jrdr.linux@gmail.com>
---
 fs/dax.c            | 78 +++++++++++++++++++++++++----------------------------
 include/linux/dax.h |  4 +--
 2 files changed, 39 insertions(+), 43 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index aaec72de..3483237 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -905,12 +905,12 @@ static int dax_iomap_pfn(struct iomap *iomap, loff_t pos, size_t size,
  * If this page is ever written to we will re-fault and change the mapping to
  * point to real DAX storage instead.
  */
-static int dax_load_hole(struct address_space *mapping, void *entry,
+static vm_fault_t dax_load_hole(struct address_space *mapping, void *entry,
 			 struct vm_fault *vmf)
 {
 	struct inode *inode = mapping->host;
 	unsigned long vaddr = vmf->address;
-	int ret = VM_FAULT_NOPAGE;
+	vm_fault_t ret = VM_FAULT_NOPAGE;
 	struct page *zero_page;
 	void *entry2;
 	pfn_t pfn;
@@ -929,7 +929,7 @@ static int dax_load_hole(struct address_space *mapping, void *entry,
 		goto out;
 	}
 
-	vm_insert_mixed(vmf->vma, vaddr, pfn);
+	ret = vmf_insert_mixed(vmf->vma, vaddr, pfn);
 out:
 	trace_dax_load_hole(inode, vmf, ret);
 	return ret;
@@ -1112,7 +1112,7 @@ int __dax_zero_page_range(struct block_device *bdev,
 }
 EXPORT_SYMBOL_GPL(dax_iomap_rw);
 
-static int dax_fault_return(int error)
+static vm_fault_t dax_fault_return(int error)
 {
 	if (error == 0)
 		return VM_FAULT_NOPAGE;
@@ -1132,7 +1132,7 @@ static bool dax_fault_is_synchronous(unsigned long flags,
 		&& (iomap->flags & IOMAP_F_DIRTY);
 }
 
-static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
+static vm_fault_t dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			       int *iomap_errp, const struct iomap_ops *ops)
 {
 	struct vm_area_struct *vma = vmf->vma;
@@ -1145,18 +1145,18 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	int error, major = 0;
 	bool write = vmf->flags & FAULT_FLAG_WRITE;
 	bool sync;
-	int vmf_ret = 0;
+	vm_fault_t ret = 0;
 	void *entry;
 	pfn_t pfn;
 
-	trace_dax_pte_fault(inode, vmf, vmf_ret);
+	trace_dax_pte_fault(inode, vmf, ret);
 	/*
 	 * Check whether offset isn't beyond end of file now. Caller is supposed
 	 * to hold locks serializing us with truncate / punch hole so this is
 	 * a reliable test.
 	 */
 	if (pos >= i_size_read(inode)) {
-		vmf_ret = VM_FAULT_SIGBUS;
+		ret = VM_FAULT_SIGBUS;
 		goto out;
 	}
 
@@ -1165,7 +1165,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 
 	entry = grab_mapping_entry(mapping, vmf->pgoff, 0);
 	if (IS_ERR(entry)) {
-		vmf_ret = dax_fault_return(PTR_ERR(entry));
+		ret = dax_fault_return(PTR_ERR(entry));
 		goto out;
 	}
 
@@ -1176,7 +1176,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	 * retried.
 	 */
 	if (pmd_trans_huge(*vmf->pmd) || pmd_devmap(*vmf->pmd)) {
-		vmf_ret = VM_FAULT_NOPAGE;
+		ret = VM_FAULT_NOPAGE;
 		goto unlock_entry;
 	}
 
@@ -1189,7 +1189,7 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	if (iomap_errp)
 		*iomap_errp = error;
 	if (error) {
-		vmf_ret = dax_fault_return(error);
+		ret = dax_fault_return(error);
 		goto unlock_entry;
 	}
 	if (WARN_ON_ONCE(iomap.offset + iomap.length < pos + PAGE_SIZE)) {
@@ -1219,9 +1219,9 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			goto error_finish_iomap;
 
 		__SetPageUptodate(vmf->cow_page);
-		vmf_ret = finish_fault(vmf);
-		if (!vmf_ret)
-			vmf_ret = VM_FAULT_DONE_COW;
+		ret = finish_fault(vmf);
+		if (!ret)
+			ret = VM_FAULT_DONE_COW;
 		goto finish_iomap;
 	}
 
@@ -1257,23 +1257,20 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 				goto error_finish_iomap;
 			}
 			*pfnp = pfn;
-			vmf_ret = VM_FAULT_NEEDDSYNC | major;
+			ret = VM_FAULT_NEEDDSYNC | major;
 			goto finish_iomap;
 		}
 		trace_dax_insert_mapping(inode, vmf, entry);
 		if (write)
-			error = vm_insert_mixed_mkwrite(vma, vaddr, pfn);
+			ret = vmf_insert_mixed_mkwrite(vma, vaddr, pfn);
 		else
-			error = vm_insert_mixed(vma, vaddr, pfn);
+			ret = vmf_insert_mixed(vma, vaddr, pfn);
 
-		/* -EBUSY is fine, somebody else faulted on the same PTE */
-		if (error == -EBUSY)
-			error = 0;
-		break;
+		goto finish_iomap;
 	case IOMAP_UNWRITTEN:
 	case IOMAP_HOLE:
 		if (!write) {
-			vmf_ret = dax_load_hole(mapping, entry, vmf);
+			ret = dax_load_hole(mapping, entry, vmf);
 			goto finish_iomap;
 		}
 		/*FALLTHRU*/
@@ -1284,12 +1281,12 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	}
 
  error_finish_iomap:
-	vmf_ret = dax_fault_return(error) | major;
+	ret = dax_fault_return(error) | major;
  finish_iomap:
 	if (ops->iomap_end) {
 		int copied = PAGE_SIZE;
 
-		if (vmf_ret & VM_FAULT_ERROR)
+		if (ret & VM_FAULT_ERROR)
 			copied = 0;
 		/*
 		 * The fault is done by now and there's no way back (other
@@ -1302,12 +1299,12 @@ static int dax_iomap_pte_fault(struct vm_fault *vmf, pfn_t *pfnp,
  unlock_entry:
 	put_locked_mapping_entry(mapping, vmf->pgoff);
  out:
-	trace_dax_pte_fault_done(inode, vmf, vmf_ret);
-	return vmf_ret;
+	trace_dax_pte_fault_done(inode, vmf, ret);
+	return ret;
 }
 
 #ifdef CONFIG_FS_DAX_PMD
-static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
+static vm_fault_t dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
 		void *entry)
 {
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
@@ -1348,7 +1345,7 @@ static int dax_pmd_load_hole(struct vm_fault *vmf, struct iomap *iomap,
 	return VM_FAULT_FALLBACK;
 }
 
-static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
+static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			       const struct iomap_ops *ops)
 {
 	struct vm_area_struct *vma = vmf->vma;
@@ -1358,7 +1355,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	bool sync;
 	unsigned int iomap_flags = (write ? IOMAP_WRITE : 0) | IOMAP_FAULT;
 	struct inode *inode = mapping->host;
-	int result = VM_FAULT_FALLBACK;
+	vm_fault_t result = VM_FAULT_FALLBACK;
 	struct iomap iomap = { 0 };
 	pgoff_t max_pgoff, pgoff;
 	void *entry;
@@ -1509,7 +1506,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 	return result;
 }
 #else
-static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
+static vm_fault_t dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
 			       const struct iomap_ops *ops)
 {
 	return VM_FAULT_FALLBACK;
@@ -1529,7 +1526,7 @@ static int dax_iomap_pmd_fault(struct vm_fault *vmf, pfn_t *pfnp,
  * has done all the necessary locking for page fault to proceed
  * successfully.
  */
-int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
+vm_fault_t dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
 		    pfn_t *pfnp, int *iomap_errp, const struct iomap_ops *ops)
 {
 	switch (pe_size) {
@@ -1553,14 +1550,14 @@ int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
  * DAX file.  It takes care of marking corresponding radix tree entry as dirty
  * as well.
  */
-static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
+static vm_fault_t dax_insert_pfn_mkwrite(struct vm_fault *vmf,
 				  enum page_entry_size pe_size,
 				  pfn_t pfn)
 {
 	struct address_space *mapping = vmf->vma->vm_file->f_mapping;
 	void *entry, **slot;
 	pgoff_t index = vmf->pgoff;
-	int vmf_ret, error;
+	vm_fault_t ret;
 
 	xa_lock_irq(&mapping->i_pages);
 	entry = get_unlocked_mapping_entry(mapping, index, &slot);
@@ -1579,21 +1576,20 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
 	xa_unlock_irq(&mapping->i_pages);
 	switch (pe_size) {
 	case PE_SIZE_PTE:
-		error = vm_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
-		vmf_ret = dax_fault_return(error);
+		ret = vmf_insert_mixed_mkwrite(vmf->vma, vmf->address, pfn);
 		break;
 #ifdef CONFIG_FS_DAX_PMD
 	case PE_SIZE_PMD:
-		vmf_ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
+		ret = vmf_insert_pfn_pmd(vmf->vma, vmf->address, vmf->pmd,
 			pfn, true);
 		break;
 #endif
 	default:
-		vmf_ret = VM_FAULT_FALLBACK;
+		ret = VM_FAULT_FALLBACK;
 	}
 	put_locked_mapping_entry(mapping, index);
-	trace_dax_insert_pfn_mkwrite(mapping->host, vmf, vmf_ret);
-	return vmf_ret;
+	trace_dax_insert_pfn_mkwrite(mapping->host, vmf, ret);
+	return ret;
 }
 
 /**
@@ -1606,8 +1602,8 @@ static int dax_insert_pfn_mkwrite(struct vm_fault *vmf,
  * stored persistently on the media and handles inserting of appropriate page
  * table entry.
  */
-int dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
-			  pfn_t pfn)
+vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
+		enum page_entry_size pe_size, pfn_t pfn)
 {
 	int err;
 	loff_t start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
diff --git a/include/linux/dax.h b/include/linux/dax.h
index f9eb22a..7fddea8 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -124,8 +124,8 @@ ssize_t dax_iomap_rw(struct kiocb *iocb, struct iov_iter *iter,
 		const struct iomap_ops *ops);
 int dax_iomap_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
 		    pfn_t *pfnp, int *errp, const struct iomap_ops *ops);
-int dax_finish_sync_fault(struct vm_fault *vmf, enum page_entry_size pe_size,
-			  pfn_t pfn);
+vm_fault_t dax_finish_sync_fault(struct vm_fault *vmf,
+		enum page_entry_size pe_size, pfn_t pfn);
 int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
 int dax_invalidate_mapping_entry_sync(struct address_space *mapping,
 				      pgoff_t index);
-- 
1.9.1

             reply	other threads:[~2018-04-21 17:14 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-21 17:14 Souptick Joarder [this message]
2018-04-21 20:17 ` [PATCH v2] fs: dax: Adding new return type vm_fault_t Matthew Wilcox
2018-04-23  5:28 ` kbuild test robot
2018-04-23  6:23   ` Souptick Joarder
2018-04-23  7:40 ` kbuild test robot

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180421171442.GA17919@jordon-HP-15-Notebook-PC \
    --to=jrdr.linux@gmail.com \
    --cc=linux-fsdevel@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=mawilcox@microsoft.com \
    --cc=ross.zwisler@linux.intel.com \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).